RESUMO
Increased atmospheric CO2 and consequent increases in temperature are two prominent features of climate change, a major challenge to crops. Here, our objectives were to determine: (1) the responses of sugarcane during the first 90 days of elevated CO2 (ECO2 ) and elevated temperature (ETem), both individually and together, and (2) the genotypic variation of these responses. Eight varieties were grown both in open-top chambers in a factorial combination of ambient/ECO2 concentrations (344-351/777-779 ppm) and ambient/ETem (34.9-35.6/36.6-38.4°C) and in open fields. Significant treatment × variety interaction effects were observed on leaf net photosynthetic rate (An ), stomatal conductance (gs ), transpiration rate (El ), and instantaneous transpiration efficiency (TE ). In most varieties, ECO2 alone did not affect An, but the combination of ECO2 and ETem decreased An . ECO2 decreased gs and El while increasing TE in all varieties. These effects were amplified when ETem was combined with ECO2 . ETem alone had variable effects on An and gs depending on variety, while it increased El and did not affect TE in a majority of varieties. Germination, tillering and stem diameter were not affected by treatments and did not show varietal variation. Leaf water potential, chlorophyll (spad), leaf area, and aboveground dry weight per plant showed varietal variations but were not affected by treatments. The variable responses to ETem and the significant genotypic variation to ECO2 and elevated temperature (ETem) observed in this work, both individually and together, demonstrate a considerable scope to breed sugarcane varieties for a future high-CO2 and warmer climate.
